There has been well known that a mechanical seal having a rotary sealing ring which is fixed to a rotary shaft body (such as a rotary shaft) rotatably driven and a stationary sealing ring which is movably held to a tubular case body (such as a seal case through which a rotary shaft concentrically penetrates) in an axial direction so as to seal the space between inner and outer peripheral areas of a relative rotation portion by means of the relative rotation of opposite end faces of both sealing rings (for example, refer to JP-A-2003-314703).
In such a mechanical seal, it is studied in a manner that ensures (that is, permits a relative movement within a predetermined range in the axial direction with respect to the case body) the following capability of the stationary sealing ring and that prevents the relative rotation of the drive pin on the case body by forming a recessed portion in the outer peripheral portion of the stationary sealing ring, attaching a drive pin to the case body by screwing or press-fitting the base end of the drive pin into a screwed hole or press-fitted hole formed in the case body, and engaging a front end of the drive pin with the recessed portion of the stationary sealing ring so as to relatively move in the axial direction (for example, refer to FIG. 1, and a second paragraph of paragraph number 0023 and a fifth paragraph of paragraph number 0025 of Patent Document 1).
Patent Document 1: Japanese Patent Application Publication No. 2003-314703
However, in a mechanism which prevents the rotation of such stationary sealing ring by the drive pin, since the drive pin is only cantilever-supported to the case body, it is difficult to effectively obtain a good mechanical seal during long terms, and following problems occur.
That is, since the base end of the drive pin is only screwed or press-fitted into the screwed hole or press-fitted hole formed in the case body, when a bending moment is applied to the front end engaging with the stationary sealing ring, it has a problem that a slack occurs between the base end and the screwed hole or press-fitted hole, and the drive pin is bended. Accordingly, the rotary prevention function of the stationary sealing ring (hereinafter, referred as “the function of the drive pin”) is obtained by means of the drive pin. With the above described state, the sealing function is not adequately realized by the relative rotation of both the stationary sealing ring and the rotary sealing ring. In addition, if the drive pin is continuously used with such state, the drive pin tends to detach from the case body, and the base end of the drive pin which is screwed or press-fitted into the screwed hole or the press-fitted hole becomes damaged and broken. As a result, since the function of the drive pin is completely lost, the sealing function cannot be realized.
As above described, even though the drive pin is a small component in all of the mechanical seals and the function (the function of the drive pin) thereof may be overlooked, the drive pin has a significant effect on the sealing function of the mechanical seal. Therefore, if the function of the drive pin is lost, it requires that all the mechanical seals be replaced or repaired. Such problems are especially prominent in the mechanical seal device such as a multi-flow channel type rotary joint in which a plurality of the mechanical seals is juxtaposed. The reason is that a functional deterioration and loss of the drive pin in one mechanical seal is directly associated with the function deterioration and loss of the overall mechanical seal device.
In addition, as the above described, since the drive pin is only cantilever-supported to the case body, the drive pin must be configured by a metal having a high stiffness with respect to strength. Therefore, since the drive pin could be not applied to a situation in which a fluid contacting with the drive pin and metal ions should not be mixed, it has the problem that the use of the drive pin is considerably limited (For example, the mechanical seal used in a rotary equipment such as a surface polishing device for polishing semiconductor wafers by CMP (Chemical Mechanical Polishing) method, which requires a steps to prevent a high contamination).
The invention has been made in consideration of the above circumstances. It is therefore an object of the invention to provide a mechanical seal and a mechanical seal device which can effectively realize the function of the drive pin and can use a plastic material capable of preventing the contamination as the component of the drive pin.